The invention relates to a device for pressing at least an area of packaging, which, at least over areas thereof, is formed of a multilayer composite material, and in which a pressing tool has at least one contour element which can be moved into an interior of the packaging, and at least one pressing element which is arranged on the outside in relation to the interior and located opposite the contour element, and in which the pressing element and the contour element are arranged so as to be capable of positioning relative to each other.
Moreover, the invention relates to a method for pressing at least an area of packaging, which is composed, at least over areas thereof, of a multilayer composite material, and in which, for carrying out the pressing procedure, at least one contour element of a pressing tool is inserted into an interior of the packaging, and in which at least one pressing element is used which is arranged on the outside in relation to the interior and is located opposite the contour element, and in which the pressing element and contour element are positioned relative to each other.
In the manufacture of multilayer composite packaging, for example, beverage packaging, different methods are used. If the manufacture is carried out from an endless composite material web or, by means of so called “hose forming machines,” the packaging bottom is only manufactured after filling and closing the packaging. However, if the manufacture is carried out from individual blanks of a cardboard/plastic composite material, these blanks are initially provided with a longitudinal seam, which as a rule, is done by the manufacturer. The longitudinal seams are produced by folding a longitudinal border of the packaging material. They have the purpose to ensure that, for example, a beverage to be filled into packaging does not come into contact with open edges of the composite material. Such a contact could lead to softening of the packaging material and a reduced lifespan of a foodstuff contained in the packaging. The manufacture of the package bottom takes place on the blanks provided with a longitudinal seam, the so called “packaging casings” only directly prior to the filling procedure, usually directly into the filling machine.
For manufacturing the package bottoms, the separated and possibly pre-folded packaging casings are usually pushed onto mandrels of a mandrel wheel, wherein the mandrels are arranged uniformly distributed over the circumference of a mandrel wheel shaft. Depending on the number of processing stations arranged around the mandrel wheel, a timed rotation of the mandrel wheel takes place. If four mandrels are present, the packaging material is pushed on in a first station, and, after a 90° rotation the folding of the packaging bottoms takes place in a second station. After folding the packaging bottoms, several layers of composite material lie, at least over sections, on top of each other.
After a further 90° rotation, the flatly folded packaging bottom is then sealed in the third station by forming the layers which are placed one on top of the other with the synthetic material of the composite material which has been softened under an increased temperature by means of pressure into a packaging bottom having a standing area. Layers of the packaging bottom which, due to folding of the bottom are located above each other, are pressed with the surface of a suitable device from the outer side of the bottom against the mandrel which rests against the inner side of the bottom. The exerted pressure leads, because of the synthetic material being softened as a result of the heat, to a pressing together of the layers and a sealing of the bottom.
The heating of the layers necessary for pressing and sealing can be effected, for example, prior to folding of the packaging bottom. However, it is also conceivable that heating of the synthetic material takes place after folding of the packaging bottom. In addition, by pressing and sealing the packaging bottom, a slight concave shape is formed toward the inner side of the bottom which imparts an especially good stability.
After sealing, the packaging bottom is cooled in order to harden the softened synthetic material in the desired shape. This can take place in the above-described sealing station or also in a separate station. Finally, the finished packaging which is open on one side is pulled from the mandrel of the mandrel wheel and supplied to the actual filling machine, where the packaging interior is cleaned and possibly disinfected and filling and closing of the finished packaging, as well as the shaping of the packaging head, take place.
The folded packaging bottom has, after folding, a thickness which varies over its surface area. The reason for this is that, during folding, in different areas of the bottom different quantity of layers are placed on too of each other. When pressing together and sealing the layers of the folded bottom with a plane pressing surface of a pressing device, wherein the pressing surface covers bottom areas of different thicknesses, there is the problem that different areas of the bottom are pressed and sealed with different intensity. In particular, the layers having a smaller thickness as compared to the adjacent areas are pressed together insufficiently.
For solving this problem, devices for pressing the layers of the packaging bottom are known, which in certain areas of their surface used for pressing, include pressing elements which protrude from the surface. These pressing elements are arranged on the surface of the pressing device in such a way that, when the bottom is pressed, they are assigned to those bottom areas which have a small thickness compared to the adjacent bottom areas. The pressing elements have the purpose of sufficiently pressing, and thereby sealing, the layers in these areas during the pressing procedure.
It is known to form these pressing elements as ribs with edges. However, during the use of these ribs, it may happen that the packaging bottom is damaged in actual practice. Leakages may occur as a result. In addition, the edged ribs lead to an increased contamination of the packaging bottom because dirt can easily collect in the pressing profile produced by the bottom.
Moreover, because of the folds in the area of the longitudinal seams, the bottom has a greater thickness than the adjacent areas. This must be taken into consideration when constructing the surface of the pressing device. When folding the longitudinal seams, it happens time and again that tolerances occur along the length as well as the thickness and height of the longitudinal seams. A compensation of such tolerances can be effected with the known device partially only insufficiently.
It is also already known, for achieving uniform pressing forces as well as for avoiding pressing forces which are too high, to use elastic pressure cushions which are elastically pressed in, for example, in the area of layers of the packaging which are placed on each other, and thereby reduce the application of excessive pressing forces in this area. However, in such elastic pressure cushions, the respective edges or step-like transitions in the area of the materials to be pressed together, causes an increased wear in such elastic cushions, so that, under the consideration of the required frequent replacement of such pressure cushions, as well as under consideration of the abrasion caused by wear, the use of such devices did not find acceptance.